A potentiometric sensor is used to detect and/or measure translational or rotational position (angles, fluid levels, distances, etc.). A potentiometric sensor is essentially a voltage divider comprising a sliding contact which engages a carbon film strip or other electrically resistive means, the resistive means being electrically connected to a supply voltage. The output voltage from the sensor is the voltage on the sliding contact or a proportion thereof. The position which is being detected or measured affects the position of the sliding contact relative to the resistive means, and so the value of the output voltage from the sensor can be used to provide an indication of the detected or measured position. A potential problem with such sensors is that a contact resistance may build up between the sliding contact and the resistive means, which, if undetected, can give rise to erroneous readings from the sensor.